Effects Of Different Nutrient Solution Conditions On Growth Of Lettuce Under The Artificial Light Condition

Under the LED light conditions, effects of different nutrition solution on concentrations, volumes of nutrition solution per plant and flow velocity of nutrient solution on leaf growth(leaf length, leaf width, leaf number), biomass(shoot fresh weight, shoot dry weight, root fresh weight, root dry weight)of lettuce and quality of lettuce were studied. Aimed to discuss the lettuce hydroponics technique under artificial light, provided scientific theoretical foundation and technological support. The major results were as follows:1. Under the DFT cultivation technique conditions, effects of different nutrition solution on concentrations(0.8 m S/cm、1.0 m S/cm、1.2 m S/cm、1.4 m S/cm、1.6 m S/cm、1.8 m S/cm) on growth of lettuce were studied. Results showed that plants had maximal fresh and dry weight of shoots and roots, leaf length and the number of leaves under 1.0m S/cm and 1.2 m S/cm concentration treatments; while those were lowest under 1.8 m S/cm. It can be indicated that nitrate accumulation of lettuce increased with the increase of nutrient solution concentration. Based on the comprehensive analysis, EC value in 1.0 m S/cm-1.2 m S/cm is the optimal concentration for hydroponic lettuce.2. Under the DFT cultivation technique conditions, effects of six different volumes of nutrition solution of every plant(1.0 L/plant、1.5 L/plant、2.0 L/plant、2.5 L/plant、3.0 L/plant、3.5 L/plant) on growth of lettuce were studied. Results showed that plants had maximal fresh and dry weight of shoots and roots, leaf length and leaf width under 3.5 L/plant volumes of nutrition solution treatment when nutrition solution did not flow; while those were lowest under 1.0 L/plant. When the nutrition solution flew, there were no significant difference in fresh and dry weight of shoots and roots, leaf length, leaf width and the number of leaves between six different volumes of nutrition solution treatments. By analyzing the quality of lettuce harvested, it can be indicated that vitamin C and nitrate accumulation of lettuce increased with the increase of volumes of nutrition solution when nutrition solution did not flow; those were no significant difference between six different treatments when nutrition solution flew. Comprehensive consideration, choosing the smaller volume of nutrition solution can save resources, but also can ensure high yield when nutrition solution flow.3. Under the LED light conditions, effects of five different flow velocity of nutrient solution(1.0 L/min、2.0 L/min、3.0 L/min、4.0 L/min、5.0 L/min) on growth of lettuce were studied when fertilizer consumption was same and nutrient solution concentration was different. Results showed that plants had maximal fresh and dry weight of shoots, leaf width, leaf number under 2.0 L/min、3.0 L/min、4.0 L/min flow velocity of nutrient solution treatments; while those were lowest under 5.0 L/min. And plants had maximal fresh and dry weight of roots under 1.0 L/min、2.0 L/min treatments; while those were lowest under 5.0 L/min. By analyzing the quality of lettuce harvested, it can be indicated that vitamin C content was lowest under 5.0 L/min, no difference between the rest of treatments; nitrate accumulation increased with the increase of flow velocity of nutrient solution. Comprehensive results showed that it can achieve the purpose of reducing nutrient solution concentration by increasing the velocity under a certain fertilizer rate. So it can reduce the pressure of nutrient fluid waste recycling. In this experiment conditions, the range of 2.0 to 4.0 L/min is the best velocity of NFT hydroponic lettuce.